Step mash rest AFTER lautering?

[McKnuckle]

Hang on... let me explain.

Let's say one conducts a two step mash, with the first 30 minutes at 145ºF for beta amylase and subsequent 30 minutes at 160ºF for alpha (one hour total). Normally we would achieve this either by applying direct heat, or adding boiling water, to raise the temperature.

But my understanding is that once starches become soluble, all the enzymatic action is taking place in the liquid wort itself. So beyond a certain point - to extract flavor - are the grain solids actually important? Can we lauter after the first rest, then raise the temp of the liquid wort to achieve a second rest?

The reason this might be practical is if one does a full volume mash in a cooler, where adding heat is basically impossible without messing with volumes. Why not drain into the boil kettle, then raise temp to 160º and hold for a period before boiling?

What am I missing in proposing this approach?

 

[Rev2010]

I think that wouldn't work well because yes, most of the enzymes are in the liquid mash. Direct heating temp is going to be much higher at the contact surface than the averaged temperature in the liquid so I'm thinking there's a much higher chance of denaturing the enzymes than you have if you do a normal decoction (remove a portion of mostly grains and boil and return to the mash to raise temp as opposed to heating all just liquid). Also, what about all the wort left behind in the grainbed? Are you not going to extract it with a sparge?


Rev.

 

[McKnuckle]

Don’t worry about the heating or grain bed in my case. I mash in a bag and drain everything; there’s no wort left behind other than standard absorption. And let’s assume that heating can occur fairly evenly with stirring. I use an induction cooktop so it can be a gentle rise.

Sounds like you’re confirming my belief that I can rest the liquid wort and achieve a similar result to a traditional mash rest.

 

[McKnuckle]

Double post

 

[doug293cz]

The bogey in this idea is that some of the starch will not gelatinize at lower temperature mash rests. So, you would not get the benefit of the additional soluble starch that might be obtained with the grain in place during the higher temp rests.

Brew on

 

[Vale71]

Starch gelatinization does not mean that starch instantly goes into solution like sugar does. Grains do not disappear as soon as gelatinization occurs, conversion still has to take place and only then can you wash as much of the extract as possible given your equipment from the grains. If you were to do like you suggest you would indeed get full conversion but your efficiency would be much lower.

 

[ccous]

Gelatinization and saccharification will both be occurring at 145F. Half an hour to 45 mins should be enough time for full conversion. So I think if you then pull the grains and are able to gently heat and hold the wort at 160, you’re essentially still mashing and can carry out that step. Never thought about it, but I feel it could be feasible.

 

[McKnuckle]

...some of the starch will not gelatinize at lower temperature mash rests.

Really? How about beers that are mashed entirely at a beta rest temperature, perhaps for 90 minutes or more to ensure conversion, since beta amylase works slowly?

If full conversion is dependent on having all available starch be accessible, and if we don't gelatinize all the starch, then we can never achieve full conversion. This seems counter to what some brewers claim (cue @RM-MN) w.r.t. the speed of conversion.

Or are we saying that "full conversion" simply means converting all soluble starch - while some may be still tied up in the grains? That seems counter-intuitive to me so I doubt it.

(Note: interesting article here, which seems to support what you're saying, albeit near the end)

For background on this post, I'm planning to brew a hefeweizen. I'm comparing the merits of a single 60 minute infusion rest at, say, 152º, with what I suggested in the original post - 30 minutes at 145º, lauter, then 30 minutes at 160º (wort only). I could re-factor the recipe volumes to incorporate a second water infusion, but I thought to propose this idea first.